Voltage overload arrester for high-voltage switching systems

ABSTRACT

A high-voltage switching system voltage overload arrester of the type including a metallic arrester housing containing a gaseous insulating medium, spark gaps and voltage dependent discharge resistors coupled in series thereto, and an electrically nonconductive housing disposed within the arrester housing, in which the spark gaps and resistors, and another gaseous insulating medium, are disposed. The improvement comprises a conductive diaphragm disposed over at least one end of the nonconductive housing which is electrically coupled to the arrester housing and discharge resistors. The diaphragm is fastened to the nonconductive housing about the periphery thereof by means of a gas-impermeable metallic solder joint, and prevents the intermixture of the gaseous insulating mediums contained in the arrester and nonconductive housings.

United States Patent 11 1 Jakszt 1 1 VOLTAGE OVERLOAD ARRESTER FORHIGH-VOLTAGE SWITCHING SYSTEMS [75] Inventor: Werner Jakszt, Berlin,Germany [73] Assignee: Siemens Aktiengesellschaft, Munich.

Germany 22 Filed: Sept. 17, 1973 211 Appl. No.: 397,921

1 1 June 24, 1975 Olsen 317/70 Kessler i. 317/62 [57] ABSTRACT Ahigh-voltage switching system voltage overload arrester of the typeincluding a metallic arrester housing containing a gaseous insulatingmedium, spark gaps and voltage dependent discharge resistors coupled inseries thereto, and an electrically nonconductive hous ing disposedwithin the arrester housing, in which the spark gaps and resistors, andanother gaseous insulating medium, are disposed. The improvementcomprises a conductive diaphragm disposed over at least one end of thenonconductive housing which is electrically coupled to the arresterhousing and discharge resistors. The diaphragm is fastened to thenonconductive housing about the periphery thereof by means of agas-impermeable metallic solder joint, and prevents the intermixture ofthe gaseous insulating mediums contained in the arrester andnonconductive housings.

3 Claims, 2 Drawing Figures VOLTAGE OVERLOAD ARRESTER FOR HIGH-VOLTAGESWITCHING SYSTEMS BACKGROUND OF THE INVENTION 1. Field of the InventionThe invention relates generally to voltage overload arresters forhigh-voltage switching systems, and in particular, to an improvedgas-impermeable housing for the components of such overload arresters.

2. Description of the Prior Art High-voltage switching systems of thetype utilizing metallic switching housings containing gaseous insulatingmediums are generally protected from voltage overloads by arrestingdevices which are disposed either within the switching system housing oroutside thereof, the latter type of which are generally connected to theswitching system by electrically conductive feedthrough couplings.Problems are presented by installations of the latter type which use agaseous insulating medium in the arrester housing which has a difl'erentdielectric strength than that utilized in the switching system housing.The gaseous atmosphere in the arrester housing must be maintained at aconstant level to insure proper functioning of the spark gaps thereinand a constant voltage response threshold level for the overloadarrester. Optimum operation of the spark gaps of the arrester occurs ina gaseous insulating medium consisting of nitrogen, whereas optimumoperation of the switching system occurs in an electronegative gaseousinsulating medium having a higher dielectric strength, such as, forexample, sulfur hexafluoride. In an arrester of the type in which thespark gaps and current discharge resistors thereof are contained in aseparate, electrically nonconductive housing disposed within an outermetallic arrester housing connected to the switching system housing, thethreshold response level of the arrester can be altered if theinsulating gas contained in the switching system housing escapes intothe nonconductive housing. It is thus desirable to provide agas-impermeable nonconductive housing to prevent variations in thethreshold response level of the arrester due to contamination of thegaseous insulating medium contained therein.

SUMMARY OF THE INVENTION It is therefore an object of the invention toprovide an improved voltage overload arrester for high voltage switchingsystems which overcomes the aforementioned disadvantages of heretoforeknown devices. This object is achieved by a high -voltage switchingsystem voltage overload arrester of the type including a metallicarrester housing containing a gaseous insulating medium, spark gaps andvoltage dependent current discharge resistors coupled in series thereto,and an electrically nonconductive housing disposed within the arresterhousing in which the spark gaps and resistors are disposed. Theimprovement comprises a conductive diaphragm, electrically coupled tothe discharge resistors and the arrester housing disposed over at leastone end of the nonconductive housing and fastened thereto about theperiphery of the diaphragm by a metallic gasimpermeable solder joint.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross-sectional view, inschematic form, of an improved high-voltage switching system voltageoverload arrester constructed according to the invention; and

FIG. 2 is a partial, cross-sectional view of one end of the improvedarrester constructed according to the invention.

It should be noted that the components of the arrester illustrated inFIG. 2 are not proportional in dimension and have been illustrated inenlarged form in order to simplify the drawings and the followingdetailed description.

DETAILED DESCRIPTION Referring now to the drawings, in particular FIG.I, there is shown a voltage overload arrester 5 comprising anelectrically nonconductive annular housing 10 in which spark gaps 7 andvoltage dependent current discharge resistors 8 coupled in seriesthereto are disposed. The structure and operation of the spark gaps anddischarge resistors are known in the art and will therefore not bediscussed herein. The spark gaps and resistors are coupled by means of acoupling conductor 27 at one end of housing 10 to a metallic arresterhousing 4 in which a gaseous insulating medium, preferably sulfurhexafluoride, is disposed. Housing 10 preferably contains nitrogen gas.The other end of arrester 5 is coupled by a feedthrough coupling member6 and another conductor 28 to a bus bar 2 disposed within a metallicswitching housing 1 and supported on an electrically nonconductivemember 3. Housing I is also preferably filled with sulfur hexafluoridegas as an insulating medium.

Referring now to FIG. 2, housing 10 of the arrester is constructed ofelectrically nonconductive material, such as, for example, porcelain,and includes radially outwardly extending rib members 11. Spark gaps 7and resistors 8 are disposed within housing I0 and connected asillustrated in FIG. I. A diaphragm 14, comprising a layer of metallic,electrically conductive material, is disposed over one end of housing 10and is separated from the end face 13 thereof by a layer of metallicmaterial 15. The diaphragm is fastened to housing 10 by means of agas-impermeable solder joint 16 disposed about the periphery thereof.The diaphragm may comprise, for example, a layer of chrome-nickel steelwhich is approximately several tenths of a millimeter in thickness.Layer 15 may comprise a layer of silver formed by applying a pastecontaining silver metal to ceramic housing 10 and firing the paste at ahigh temperature to securely fasten the silver to the housing. Thediaphragm is soldered by means of soft or hard solder to the metallicsilver layer. lf housing 10 is constructed of material other thanprocelain, such as organic insulating material, a metallic ring or metalfitting can be embedded into the housing by casting or other knownmethods when the latter is fabricated so that a suitable solderingsurface is provided for fastening the diaphragm to the housing.

An annular rubber seal 17 is disposed on the other side of diaphragm l4and separates a metallic cap 20, which is disposed over the end ofhousing 10 and is attached thereto by a cement joint 21, from thediaphragm. The cap and seal 17 press diaphragm 14 against metal layer 15and end face 13 and additionally secure the diaphragm on the housing.The arrangement also causes expansion of the diaphragm to be absorbed byfriction so that solder joint 16 is not affected. Metallic cap 20 iselectrically coupled to housing 4, and to ground potential throughhousing 1, by conductor 27 (not shown in FIG. 2). Electrical contacts 22and 23 are mounted on resistors 8 and seal 17 by suitable fasteningmeans and electrically couple the diaphragm to the discharge resistorsand housing cap 20. A rivet 29 secures a conductive cover 24 to cap 20which electrically couples contact 22 thereto.

The diaphragm also functions as a pressure relief mechanism for thearrester housing. Diaphragms have heretofore been used as pressurerelief devices, but have merely been pressed against the end faces ofarrester housings on an interdisposed sealing ring, and a gas-tightpressure resistant seal sufficient to function as described hereincannot be obtained. Cover 24 is fastened to cap 20 by rivet 29, which isof the release type, and covers an opening provided in the cap for theescape of gas. If excessive pressure builds up in housing l0, theresultant gas pressure ruptures diaphragm 14 and cover 24. The gasescapes through nozzles 25 formed over cap 20 by a deflection plate 26attached to the cap by mounting members 12. It should be noted thatalthough only one end of housing has been illustrated as being sealed bythe diaphragm arrangement described herein, the same seal may beprovided at either or both ends of housing 10 to effect the requiredgas-tight sealing of the housing.

While there has been disclosed herein what is considered to be apreferred embodiment of the invention, it will be understood by thosepersons skilled in the art that many changes and modifications may bemade thereunto without departing from the invention. It is thereforeintended in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What is claimed is: i

1. In a high-voltage switching system voltage overload arrester, of thetype including a metallic arrester housing containing a gaseousinsulating medium, spark gaps and voltage dependent current dischargeresistors coupled in series thereto, and an electrically nonconductivehousing, containing another gaseous insulating medium, disposed withinthe arrester housing, in which the spark gaps and resistors aredisposed, the improvement comprising a diaphragm comprising a layer ofelectrically conductive metallic material, electrically coupled to saidarrester housing and discharge resistors, and disposed over at least oneend of said nonconductive housing and fastened thereto about theperiphery of said diaphragm by a metallic gas-impermeable solder joint,said solder joint comprising a layer of metallic material fastened to anend face of said nonconductive housing and solder material joining saiddiaphragm to said layer of metallic material; a rubber seal engagingsaid diaphragm; and a metallic cap, disposed over the endface of saidnonconductive housing and secured thereto by a cement joint, and spacedapart from said diaphragm by said rubber seal.

2. The overload arrester recited in claim 1, further comprisingelectrical contacts coupled to said discharge resistors and said cap anddisposed in engagement with said diaphragm.

3. The overload arrester recited in claim 1, further comprising adeflection plate, mounted on said cap and spaced apart therefrom so asto form nozzles therebetween, and a breakable, electrically conductivecover. fastened to said cap and disposed over an opening providedtherein.

* i I l l

1. In a high-voltage switching system voltage overload arrester, of thetype including a metallic arrester housing containing a gaseousinsulating medium, spark gaps and voltage dependent current dischargeresistors coupled in series thereto, and an electrically nonconductivehousing, containing another gaseous insulating medium, disposed withinthe arrester housing, in which the spark gaps and resistors aredisposed, the improvement comprising a diaphragm comprising a layer ofelectrically conductive metallic material, electrically coupled to saidarrester housing and discharge resistors, and disposed over at least oneend of said nonconductive housing and fastened thereto about theperiphery of said diaphragm by a metallic gasimpermeable solder joint,said solder joint comprising a layer of metallic material fastened to anend face of said nonconductive housing and solder material joining saiddiaphragm to said layer of metallic material; a rubber seal engagingsaid diaphragm; and a metallic cap, disposed over the endface of saidnonconductive housing and secured thereto by a cement joint, and spacedapart from said diaphragm by said rubber seal.
 2. The overload arresterrecited in claim 1, further comprising electrical contacts coupled tosaid discharge resistors and said cap and disposed in engagement withsaid diaphragm.
 3. The overload arrester recited in claim 1, furthercomprising a deflection plate, mounted on said cap and spaced aparttherefrom so as to form nozzles therebetween, and a breakable,electrically conductive cover, fastened to said cap and disposed over anopening provided therein.